Messages in this thread | | | Date | Thu, 27 Mar 2008 15:11:15 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: Trying to make use of hotplug memory for xen balloon driver |
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On Wed, 26 Mar 2008 22:57:57 -0700 Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> Ah, I see what it is. I wasn't trying to add enough memory. It adds in > units of SECTION_SIZE_BITS, which is 2^30 on 32-bit PAE. When I > increase the initial balloon extension to PAGES_PER_SECTION pages, I > make some more progress: > > xen_balloon: Initialising balloon driver. > trying to reserve 262144 pages (1073741824 bytes) for balloon > bootmem alloc of 147456 bytes failed! > Kernel panic - not syncing: Out of memory > Pid: 1, comm: swapper Not tainted 2.6.25-rc7-x86-latest.git-dirty #361 > [<c01299dc>] panic+0x49/0x102 > [<c0647c3c>] __alloc_bootmem+0x24/0x29 > [<c0647c6d>] __alloc_bootmem_node+0x2c/0x34 > [<c044bd97>] zone_wait_table_init+0x45/0x95 > [<c0467258>] init_currently_empty_zone+0x1d/0xaa > [<c01738ea>] __add_pages+0x88/0xdb > [<c011c1a5>] arch_add_memory+0x25/0x2b > [<c01737a9>] add_memory_resource+0x2f/0x36 > [<c064e487>] balloon_init+0x1b8/0x2b9 > [<c0635495>] kernel_init+0x137/0x292 > [<c063535e>] ? kernel_init+0x0/0x292 > [<c063535e>] ? kernel_init+0x0/0x292 > [<c0108b67>] kernel_thread_helper+0x7/0x10 > ======================= > > > What's the rationale for setting SECTION_SIZE_BITS to 30? Seems like a > fairly large chunk. > At first, I believe usual DIMM size is bigger than SECTION_SIZE_BITS. This is designed for hardware-based hotplug.
If you want to use memory-hotplug for virtualized enviroment, it's good to make this to be smaller chunk. Powerpc/IBM lpar uses 16MB chunk.
It's a trade-off between section mainainance cost v.s. size of plugged memory. please find the best.
Thanks, -Kame
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